Indicator mechanisms having electrically controlled magnetic movements, which may be housed in small housings and readily mounted on a panel for a variety of purposes are known in the prior art. A representative sampling of prior art devices of this type may be seen in U.S. Pat. Nos. 2,836,773 and 3,936,818, both to Alfred Skrobisch ("Skrobisch 1 and 2") and 3,543,202 to Edward V. Naybor. Each patent generally discloses a rotor in the form of a permanent magnet, which may be a magnet in disc form (Skrobisch 1 discloses that the permanent magnet may be either a bar magnet or a magnet in disc form) and a stationary electromagnet.
Skrobisch 1, more particularly, discloses a device which requires only negligible power for operation of the movement (the magnet) which includes indicator indicia in the form of coated surfaces on the magnet, such as a black and white coating throughout sectors of the surface to indicate a normal or abnormal condition at a viewing window. The magnet does not latch in the energized orientation, but, rather, returns to the unenergized orientation when the operating power is discontinued.
Naybor discloses a somewhat similar device which is responsive to short duration direct current pulses, described as at least 15 milliseconds (ms) in length, and functions in a manner to latch thereby to maintain the last position achieved. Thus, Naybor discloses a bistable type of device wherein the permanent magnet which functions as a visual indicator presents one of two possible aspects.
Skrobisch 2 discloses a device, like that of Skrobisch 1 and Naybor, wherein the indicator device is in the form of an assembly including a plurality of permanent magnets and a stator subassembly providing a plurality of stationary electromagnets. Skrobisch 2 describes that the permanent magnets are arranged to latch in either one of two positions, or they may operate without latching.